A penetrating radar apparatus is one of apparatuses used for non-destructive inspection. The penetrating radar apparatus projects an RF penetration signal to a transmissive object and thereafter, receives a reflected signal to analysis an inner structure of the object.
A method in which the penetrating radar apparatus acquires the reflected signal includes an impulse scheme and a step frequency scheme.
The impulse scheme is a scheme that uses a signal having higher energy within a very short time, that is, an impulse signal as a projection signal. The projected impulse signal has a wideband frequency characteristic. Herein, as a bandwidth of a frequency is wider, the inner structure of the object can be detected with high resolution. Further, since the impulse scheme projects a wideband signal at once, the impulse scheme can generally perform sensing very rapidly.
The step frequency scheme is a scheme that senses the inner surface of the object by taking an effect such as projecting a continuous wave (CW) signal (that is, a sine wave) at a predetermined frequency interval within a specific frequency band to project the wideband signal on the whole. In the step frequency scheme, a frequency of a CW signal is divided into steps with the passage of time and raised or dropped to generate the wideband signal unlike the impulse scheme that projects the wideband signal at once, a time is required to generate one wideband signal, and as a result, sensing is performed at a much lower speed compared to the impulse scheme.
Meanwhile, the step frequency scheme has a merit in that it is advantageous in acquiring the high-resolution transmissive signal because a frequency band characteristic of the generated signal is good and the signal is generated with high power. But as described above, the step frequency scheme has a limit in being utilized efficiently due to a characteristic that only very low-speed sensing is enabled.